ME. W. H. PLOWEE ON THE OSTEOLOGY OF THE SPEEM-WHALE. 



335 



As the posterior surface of the body of the cervical vertebrae is ankylosed with 

 the first dorsal, little can be said of its characters. The centrum, however, is very 

 deeply concave, receiving the con^ ex anterior surface of that of the first dorsal ; and 

 there is a smooth articular facet {iwsterior zyga/pophysis) at each side of the neural 

 arch. This facet is more vertical (inclining less backwards at the upper end) than 

 in other Cetacea. 



Measurements of the conjoined six posterior Cervical Vertebrae. 



The Dorsal Vertehrce (Pis. LVIII. and LIX.) are eleven in number. The first ten 

 support well-developed ribs ; the eleventh, which in many of its characters resembles 

 a lumbar vertebra, has only a rudimentary pair of ribs attached to the extremity 

 of the transverse processes. The first dorsal is ankylosed by the middle part of its 

 centrum (at all events at the upper and lower margins near the middle line, where no 

 trace of a suture remains) to the hinder part of the conjomed six posterior cer- 

 vical vertebrae. The lateral parts of the centrum are free, as also is the whole of the 

 neural arch. 



The body of the first is hy very far the shortest in the antero-posterior direction ; the 

 second is nearly twice as long ; and they continue to increase gradually and progressively 

 throughout the series, as will be seen by the table of measurements. The body of the 

 first is extremely concave on its posterior aspect, the middle part being 3" deeper than 

 the sides. The second is convex in front, and concave behind to a less degi-ee. In the 

 succeeding vertebrae the anterior and posterior surfaces are nearly flat and parallel. 

 The bodies, at first very broad in proportion to their height, rapidly become narrower ; 

 in the fourth the breadth is already less than the height ; the sixth, seventh, and eighth 

 are the narrowest ; after these there is a slight increase of width. 



The neural canal in the first two vertebrae is triangular, but rapidly assumes a trans- 

 versely oval form, and gradually diminishes in both height and breadth, so much more, 

 however, in the last dimension that in the tenth vertebra the long diameter of the oval 

 is vertical ; in the eleventh the lateral contraction is still more marked. 



3 a2 



